The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:
3GPP third generation partnership project
CA carrier aggregation
CC component carrier
CE control element
CQI channel quality indicator
CRS cell specific reference signal
DL downlink (node B towards UE)
eNB node B/base station in an E-UTRAN system
E-UTRAN evolved UTRAN (LTE)
GERAN GSM EDGE Radio Access Network
GSM global system for mobile communications
ISM industrial, scientific and medical
LTE long term evolution
LTE-A LTE-Advanced
MAC medium access control
MME mobility management entity
PCC primary component carrier
PRACH physical random access channel
PSTN public switched telephone network
RACH random access channel
RRC radio resource control
RRM radio resource management
RS reference signal
RSRP reference signal received power
RSRQ reference signal received quality
RSSI received signal strength indicator
Scell secondary component carrier
SOW serving gateway
SIB system information block
TDM time division multiplex
UE user equipment
UL uplink (UE towards node B/eNB)
UTRAN universal terrestrial radio access network
WLAN wireless local area network
The LTE-Advanced wireless system is designed to provide enhanced services by means of higher data rates and lower latency with reduced cost. Carrier Aggregation (CA) is one technology to improve data rates. FIG. 1 illustrates the CA concept: the whole bandwidth of the wireless system is divided into two or more component carriers (CCs), of which FIG. 1 shows five CCs by example. At least one CC is configured to serve legacy UEs. Release 10 and later UEs are to be capable of monitoring/using multiple CCs, and so the wireless network is able to assign two or more CCs simultaneously as active for a single UE. This enables the network greater scheduling flexibility by giving it the ability to allocate channels to the same UE on any of the one or more CCs assigned to the UE. For the case that multiple CCs are assigned and active for a UE, one of the assigned CCs will be the UE's primary CC and the other(s) will be secondary CC(s). The UE's secondary CC(s) is/are also sometimes termed an extension carrier.
3GPP LTE Rel-10 uses CCs designated on a licensed band. In an LTE-A system an eNB will configure RRM measurement for a UE in a licensed band, and the UE will report related results used to decide which cell/carrier on the licensed band is good enough to be configured. An RRM measurement is based on a cell specific reference signal (CRS) measurement, but the CRS is transmitted only in the carriers already configured in an LTE system, these carriers being of the licensed band.
For at least this reason, there is no support in the LTE system for carrier aggregation using an unlicensed band. What is needed in the art is a way to intelligently deploy unlicensed spectrum for use in a CA type system. Such a deployment has the potential to reduce operator's cost, improve system throughput, off-load traffic from a licensed band, and improve spectrum efficiency overall. However, it is understood that new efficient measurement and sensing mechanisms, as well as configurations, would be required in order to achieve such potential.
Some discussion for developing the LTE-A standard for shared band access may be seen at a presentation by M-A Phan, H. Wiemann and J. Sachs entitled FLEXIBLE SPECTRUM USAGE—HOW LTE CAN MEET FUTURE CAPACITY DEMANDS (Ericsson; Jul. 8, 2010;) and another by Rui Yang entitled OVERVIEW OF RESEARCH PROJECTS WITH NYU-POLY (InterDigital Communications; Nov. 12, 2010).